Cylinder and piston assembly with automatic power release



June 17, 1969 CYLINDER AND PISTON ASSEMBLY WITH AUTOMATIC POWER RELEASE Filed Jan. 29, 1968 Sheet of 2 Idas B. Whi fe' INVENTOR.

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x062 laJ I Maw vMm United States Patent 3,450,006 CYLINDER AND PISTON ASSEMBLY WITH AUTOMATIC POWER RELEASE Idas B. White, Blountstown, Fla., assignor to Timberjack Machines Limited, Woodstock, Ontario, Canada, a corporation of Canada Filed Jan. 29, 1968, Ser. No. 701,238 Int. Cl. F!) 15/22, 11/08, 13/04 US. Cl. 91-401 3 Claims ABSTRACT OF THE DISCLOSURE The instant invention is generally concerned with a hydraulic motor or cylinder and piston assembly utilized in driving a tree shearing blade, and is more particularly concerned with a power release incorporated in the assembly so as to prevent a power driving of the blade beyond a predetermined point.

It is a primary object of the instant invention to provide unique means whereby, through a limiting of the stroke of the piston of a hydraulic motor which operates a shearing blade, the power eflecting the movement of the blade can be released, thereby enabling an automatic halting of the movement of the blade so as to prevent possible damage to the blade, the anvil or jaw against which the blade operates, and for that matter the hydraulic system itself.

In conjunction with the above object, it is also an important object of the instant invention to provide a power release wherein the point of release can be varied so as to in turn vary the stroke of the piston and consequently the stroke of the severing blade associated therewith.

Likewise, it is an important object of the instant invention to provide a valved power release which is positive acting and capable of trouble-free operation, utilizing a highly unique, while at the same time relatively simple construction.

Basically, the objects of the above invention are achieved through the utilization of a pair of laterally orientated valves mounted within the piston of a cylinder and piston assembly with one of the valves being released through physical engagement with an adjustable abutment, the released valve allowing the passage of fluid thereby and, through a diagonal fluid passage, through the second valve which is in the nature of a one-way check valve communicated with the release or exhausting side of the piston. The nature of the check valve is such so as to cause an immediate opening thereof in response to a pressure differential.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIGURE 1 is a top plan view of a tree shearing unit illustrating the general environment of the instant invention;

FIGURE 2 is an enlarged cross-sectional view through the forward end of the cylinder and piston assembly of the 3,450,006 Patented June 17, 1969 instant invention with the piston in a retracted position;

FIGURE 3 is a view similar to FIGURE 2 with the piston at the completion of its stroke and with the power release construction open;

FIGURE 4 is a cross-sectional view similar to FIGURE 3 with the assembly rotated approximately so as to illustrate the entire power release arrangement;

FIGURE 5 is a cross-sectional view taken substantially on a plane passing along line 55 in FIGURE 3; and

FIGURE 6 is a cross-sectional view illustrating the manner in which the shearing blade cooperates with a fixed jaw or anvil in effecting the tree severing or shearing.

Referring now more specifically to the drawings, reference numeral 10 is used to generally designate the hydraulic motor or cylinder and piston assembly. This assembly 10, noting FIGURE 1 in particular, will, in actual use, normally be utilized as a motivating means for a pivotally mounted tree shearing blade 12 which cooperates with a fixed jaw or anvil type blade 14 in effecting the shearing of a tree or the like 16. Because of the substantial power required in effecting the shearing movement of the blade 12 through the tree 16, the possibility of damage to the blade, blade frame, anvil or hydraulic system itself is great unless the power effecting the movement of the blade is released at the appropriate time, such of course being subsequent to the shearing of the tree and prior to the introduction of undesirable stresses to the entire assembly. However, such exacting control is frequently not possible, especially when working in heavy underbrush and the like wherein the shearing unit may not be visible from the control cab of the tractor. Accordingly, the automatic power release for the assembly 10 has been devised.

The assembly 10 is, in itself, conventional in that it includes an elongated cylinder 18 within which a piston 20 is slidably mounted. The piston 20 mounts an elongated piston rod 22 which is slidably received through a cylinder head 24 on the forward end of the cylinder 18. Suitable fluid ports 26 are in communication with the cylinder 18 adjacent both the forward head 24 and a similar head at the rear end thereof, these ports 26 in turn being in communication with a fluid or hydraulic system, through lines 28, such a system normally being mounted on an associated vehicle, such as for example the propelling tractor of FIGURE 1. Suitable sealing rnigs 30 and 32 are provided so as to enable a fluid excluding sliding movement of both the piston 20 and the rod 22, also in a substantially conventional manner.

It is the primary purpose of the instant invention to provide a power release operable as the piston 20 approaches the forward end of the stroke adjacent the cylinder head 24 under the influence of the greater pressure in the rear or high pressure chamber 34. Accordingly, the piston 20 is provided, radially of the rod 22, with a first valve passage 36 therethrough, this valve passage 36 slidably receives an elongated valve stem 38 therethrough in what amounts to a fluid tight manner. The stem 38, on the rear chamber side of the piston 20, includes an enlarged valve or valve head 40 which seats against an enlarged valve seat 42 provided in the counterbored rear end of the valve passage 36. The forward end of the valve passage is also counterbored so as to define an enlarged forwardly opening chamber 44 within which a coiled expanded compression spring 46 is seated. This spring 46 surrounds the valve stem 38 and bears, at one end thereof, against the inner end of the counterbored chamber 44 and, at the other end thereof against a washer or ring 48 aflixed to the forward end of the valve stem 38 by a suitable lock ring 50 or the like. With reference to FIGURE 2, it will be noted that when the spring 46 is in its normal stern biasing uncompressed condition, the valve head 40 is seated within the valve seat 42 in a fluid excluding manner,

3 while the forward end 52 of the stem projects forwardly of the piston 20.

With reference to FIGURE 3, it will be noted that the retraction of the valve 40 is effected through an engagement of the forward end 52 of the valve stem 38- with an abutment or abutment head 54 provided on the inner end of a threaded shaft 56 threaded through an internally threaded hole or passage 58 in the cylinder head 24. The bolt 56 is to be provided with an appropriate tool receiving head 60 on the outer end thereof and has an appropriate lock nut 62 threaded thereon and engageable against the outer face of the head 24 so as to fix the bolt 56 in its adjusted position. It will of course be appreciated that the bolt 56 is of a length so as to project both inwardly and outwardly of the cylinder head 24 so as to provide for a substantial range of adjustment, and thereby vary the point at which the valve 40 is unseated and the power released. Incidently, with reference to FIGURE 3, it will be noted that a complete unseating of the valve 40 is effected prior to engagement of the spring retaining washer 48 against the forward face of the piston 20.

Referring now to FIGURE 4, it will be noted that the actual release of the power upon an unseating of the valve 40 is effected through a diagonal fluid passage 64 which communicates the countersunk valve seat defining portion of the passage 36 with the inner end of a fluid passing bore 66 which opens through the forward face of the piston 20 and has an internally mounted one-way ball check valve 68 spring-biased, by suitable spring means 70, against a valve seat 72 defined at the communicating end of the diagonal fluid passage 64. The check valve 68 can actually be mounted in any appropriate springloaded manner within its bore 66 laterally spaced from the passage 36, as long as adequate space is provided thereabout, when open, for the passage of the released fluid from the rear or high pressure chamber to the forward or low pressure chamber. The stroke adjusting member will be adjusted so as to effect a power release through the piston 20 at a predetermined point. Thus, as the piston 20 approaches the cylinder head 24, the stem end 52 will engage the abutment head 54 and the valve 40 will be unseated. Upon the valve 40 leaving its seat the fluid from the high pressure side of the piston 20 will flow past the valve 40, through the diagonal passage 64, and, upon an automatic releasing of the one-way ball check valve 68, through the bore 66 into the rear exhaust chamber for discharge through the associated exhausting port 26. In this manner a release of power will be automatically effected and forward movement of the piston 20, as well as the associated blade 12, terminated. At this point, through a suitable control valve accessible from the cab of the tractor, the pressure on the high pressure side of the piston 20 can be relieved, this in turn resulting in an automatic and immediately closing of the check valve 68 whereby, upon the introduction of pressure into the forward chamber, a retraction of the piston 20, thereby the blade 12, can be eifected. It should be appreciated that the strength of the ball biasing spring 70 should be such so as to, while being capable of positively seating the ball 68 upon the presence of equal pressure to the opposite sides thereof, be responsive to the minimum pressure differential which will be utilized to effect the powered forward movement of the piston 20 whereby upon a retraction of the valve 40 immediate release of pressure can be effected to the forward exhaust chamber so as to avoid any delay in effecting the relieving of the piston moving pressure and the halting of the piston and'associated blade at a predetermined point defined by the adjustable abutment defining member which operates the valve assembly.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described.

What is claimed as new is as follows:

1. A cylinder and piston assembly comprising a cylinder, a forward cylinder head, a double-acting piston slid-v ably disposed within said cylinder and defining forward and rear pressure chambers for powered movement toward and away from said head by the selective introduction of pressure to the opposite sides thereof, and release means for effecting an automatic communication between said chambers through said piston upon the introduction of a high pressure in said rear chamber and movement of the piston to a predetermined point along its path of movement toward said cylinder head, said piston having forward and rear faces, said release means comprising a valve stem slidably received through said piston and projecting beyond the forward face thereof, a'valve seat defined in the rear face of said piston, a valve head on said stem, means resiliently biasing said valve head into seated engagement with said seat, a laterally directed fluid passage within said piston having a first end in fluid receiving communication with the inner end of said valve seat for reception of fluid therefrom upon an unseating of the valve head, a second fluid passage in generally laterally parallel relation to the valve stem, said second fluid passage extending from the second end of the first passage through the forward face of the piston, and check valve means in said second passage, means for resiliently biasing said check valve means to preclude movement of fluid from the forward chamber to the rear chamber, said check valve means being operable to open in response to the presence of a pressure differential upon movement of fluid under pressure into said second passage from said first passage.

2. The assembly of claim 1 wherein said release means further includes an abutment mounted on said cylinder head and projecting into said forward chamber, said abutment being engageable with said valve stem upon a forward movement of said piston for effecting an unseating of said valve head at a predetermined point along the path of movement of said piston.

3. The assembly of claim 2 including means for adjusting the amount of projection of said abutment into said forward chamber for adjusting the predetermined point at which said valve head is unseated.

References Cited UNITED STATES PATENTS 1,904,345 4/1933 Anthony et a1 91401 2,233,521 3/1941 Ernst et al. 91-401 2,265,314 12/1941 Rose 91401 2,630,830 3/1953 Meddock. 1 2,948,263 8/ 1960 Royer. 3,148,591 9/1964 Sheesley 91-401 3,173,341 3/1965 Carpenter. 3,182,563 5/1965 Neilan.

PAUL E. MASLOUSKY, Primary Examiner.

US. Cl. X.R. 91-446 

